Hepatitis B

Hepadnavirus

Hepatitis B is a circular and partially double-stranded DNA virus; enveloped,

intranuclear and cytoplasmic replication

(uses reverse transcriptase), in contrast to HIV, cannot integrate into host chromosome, so Not a Retrovirus

spread through exposure to infected blood or body fluids/sex, including vertical transmission from mother to child (cannot cross the placenta but mixing blood during delivery -> member of TORCHes).

insidious onset

The incubation period is 6-20 weeks. (30-180 days)

5-10% of adults -> chronic, however

90-90% of infected newborn -> chronic

Pathogenesis

Two phases:

The proliferative phase and the integrative phase

Proliferative phase:

viral surface antigens react with MHC I --> activate CD8+ T lymphocytes --> destroy infected hepatocytes

Integrative phase:

HBV DNA is incorporated into the host genome of those hepatocytes that survived the immune response. Infectivity ceases and liver damage tapers off when the antiviral antibodies appear and viral replication stops. The risk of HCC, however, remains elevated because of the HBV DNA that has been integrated into the host genome

Initial clinical presentation is sometimes referred to as "serum sickness-like" due to malaise, fever, lymphadenopathy,

parpuric rash with non-blenching dark macules

Arthralgias